Separation techniques such as MLC or HPLC are commonly used in analytical chemistry. These techniques offer high separation efficiency, high mass sensitivity and high resolution for the purification and separation of products of organic reactions. They are especially useful in pharmaceutical research for drug discovery. Normally, a UV cell or a light scattering cell is used for the detection of the sample. This cell is placed in line between the HPLC spectrometer and the fraction collector and is passed by the HPLC flow. However, for the identification of the substance a UV cell is not suitable. Therefore, a further detector such as a mass spectrometer is needed for the identification of the sample.
Certain detector systems require only a small amount of sample for detection and, therefore, cannot handle the relatively large sample volumes generated on a preparative scale. These detector systems require a split in the flow to divert the sample from the detector. For methods that are destructive to the sample, such as mass spectrometry and light scattering, a split in the flow is required in order to divert most of the sample to a fraction collector so that the desired materials can be collected.
Flow splitters are already known. In EP 495 255 A1 a flow splitter consisting of a micromixer and a microsplitter is described. However, the functionality that is currently available results in large broadening of the sample peaks and therefore loss of efficiency and potentially remixing of samples that would otherwise be collected in pure form.
The present invention is concerned with the problem of providing a microflow splitter system with a higher collection rate, minimized sample loss and higher resolution of the sample peak.
The invention solves this problem by providing a microflow splitter device consisting of a splitter system including a microsplitter and a micromixer which are connected by a microbore tubing. A high collection rate and high resolution of the sample peak are achieved by the proper choice of tubing length and diameters and the use of a back pressure regulator to obtain a controlled split ratio. More specifically, the present invention provides a microflow splitter device for the conversion of conventional flow rates (ml/min) into microflow rates (.mu.l/min) in microseparation techniques, particularly for the collection of HPLC sample fractions which are detected and identified by a mass spectrometer, comprising a microsplitter (2) and a micromixer (3), which are connected by a microbore tubing (4), wherein said micromixer (3) is placed after said microsplitter (2) and wherein the microsplitter (2) is connected with a wide bore tubing (8) for the flow towards the fraction collector (9) which is equipped with a back pressure regulator (19) and a filter frit (18).
In a further embodiment, the present invention is directed to a process of making a microflow splitter device for the conversion of conventional flow rates (ml/min) into microflow rates (.mu.l/min) in microseparation techniques, particularly HPLC techniques in connection with a mass spectrometer for identifying the samples, comprising the steps of:
placing a micromixer behind a microsplitter; PA1 connecting said microsplitter to said micromixer by means of a microbore tubing; PA1 connecting a wide bore tubing for the flow towards the fraction collector with the microsplitter; PA1 inserting a back pressure regulator into said wide bore tubing; and inserting a filter frit into said wide bore tubing.